Piston for internal combustion engines



June 24;, 1930; P.'PR|TCHARD 1,767,395

PISTON" FOR INTERIN'VAL COMBUSTION ENGINES Filed April 10. 1928 T INVENTORQ Patented June 24, 1930 i UNITED STATES PERCY PRITCHARD, OF SMETHWTGK,. ENGLAND PISTON FOR INTERNAL COMBUSTION, ENGINES Application filed. April 10, 1928, Serial No. $68,988, and in Great Britain May 25, 1927.

This invention relates to improvements in pistons for internal combustion engines and refers particularly to pistons of the composite type in which a head of aluminium or aluminium or magnesium alloy is combined with a skirt or wearing surface of steel or castiron.

It has been frequently proposed in such pistons to cast the head on to the'skirt or shell but it is found to be a matter of con- 1 siderable ditficulty to ensure a satisfactory key between the two parts so that no relative movement can take place even after prolonged wear. r

If the slightest looseness is present initially or develops in use it increases at a rapidly progressive rate owing to the strains to which the piston is subjected and the subsequent working life of the piston is short. I

The object of our invention is to provide a thoroughly practical and eflicient-key between the two parts of a. composite piston, and to maintain a gastight'joint between these parts, and our invention consistsin providing at the upper end of the steel, cast-iron, or other shell an inwardly projecting flange or lip of which the extremity is cranked upwardly and outwardly at an acute angle to form an inclined shoulder or step. When the aluminium or other head is cast on to the shell this flange with the,

inclined shoulder or step is wholly embedded in the metal of the head and effectively keys the two parts of the piston together. The angle of the lip being a re-entrant angle, the metal of the body or head on shrinking cannot draw away from the lip and leave a bad joint, and the lip forms a locking flange holding the aluminium or like metal on shrinking. The piston is subsequently machined where necessary and grooves to receive piston rings are out either in the head or in the shell near its upper end which may be of sufiicient thickness for this purpose. If made of steel the shell may be comparatively thin and the skirt may be in contact with or spaced from depending bosses on the head which carry the gudgeonpin.

Pistons'manufa ctured in accordance with our invention are illustrated inthe accomof the shell; V

. 1 Figure 2 is a'vertical section through a complete piston. I

Figure 3 is a section on the line 3/3 of Figure 2.

Figure 4 is a vertical section through a slightly modified form of shell.

Figure 5 is a section similar to Figure 3 but showing aconstruction in which the piston rings are carried by the head. The tubular shell a shown in Figure 1 may be of steel or cast-iron machined to the required dimensions, this particular shell being of steel and having a very thin skirt 6. The upper part is of substantial thickness to receive the grooves for the piston rings and at the upper extremity there is provided an upwardly and outwardly inclined lip or flange '0. When the head a? of aluminium or aluminium alloy is cast on to the shell the lip c is embedded in the metal of the head as shown in Figure 2 and locks the two parts together. The tubular bosses a for the gudgeon-pin are integral with the head to'which'they are connected by webs f, and, as here shown, are spaced from the skirt of the shell but this is immaterial and can be modified to suit particular design of pistons. After the casting operation the shell and head are machined to the required dimensions and the grooves g for the rings are cut in the thicker upper part of the shell.

The shell shown in Figured is suitable for manufacture in cast-iron, theskirt h being of substantial thickness, and the gudgoon-pin bosses in this case'may be in contact with theinnersurfaceof the skirt.

In the construction shown in Figure 5 the piston rings are received in grooves j cut in the cast head 70. The shell lie of uniform thickness throughout and at its upperend has an inwardly directed annular flange m having an outwardly and upwardly PATENT OFFICE a cranked lip 11, so that an acute angle is When the head is cast on to the shell the flange m and the lip n are embedded in the metal of the head below the grooves 7'.

I claim r 1. A composite piston for internal combustion engines comprising a cast metal head, a cylindrical shell on to which the head is cast, an inwardly directed annular flange at the upper end of the shell; and an upwardly and outwardly directed lip on the flange to form a re-entrant angle therewith, the flange and lip being wholly embedded in the metal of the head.

2. A composite piston for internal combustion engines comprising a cast metal head, gudgeon-pin bosses on the head, a cylindrical shell on to which the head is cast, a thickened portion at the upper end of the shell, piston-ring grooves cut in the said thickened portion, and a projecting and inclined flange on the shell wholly embedded in the metal of the head.

PERCY PRITCHARD. 

